The impact of geographic origin on the nutritional profile and protein quality of soybean meal

Global projections indicate that the world population will reach 9.7 billion by 2050, and that demand for animal protein will increase by 14% and egg consumption by 39% as a result. This massive increase in demand is further deepening dependence on key feed raw materials such as corn and soybeans. Therefore, the quality of soybean meal in animal feed is a critical issue (Ravindran et al., 2014).

Soybean production statistics

Figure 1 illustrates a continuous upward trajectory in global soybean production. Based on FAOSTAT data, an all-time production high was achieved in 2024. This momentum continued into 2025, with U.S. Department of Agriculture figures indicating that global output surged to a new record of 428.15 million metric tons. Driven by steadily climbing market demand, this pattern of annual growth is projected to persist.

The importance of soybeans in animal feed

The most important characteristic of soy is that it provides more protein per unit area and at a lower cost compared to other plant and animal feed sources. Soy protein is the protein closest to animal protein and has a very high biological value. For this reason, by-products derived from soybeans (primarily soybean meal) are used as a protein source in rations for poultry and small ruminants, as well as dairy and beef cattle (Anonymous, 2019; Tüfekçi, 2019).

The protein content of soybean meal is influenced by several factors, including soybean variety, tillage, soil properties, climate, harvest, and processing conditions (Grieshop et al., 2003; Thakur and Hurburgh, 2007; de Coca-Sinova et al., 2008; Frikha et al., 2012; Ravindran et al., 2014; García-Rebollar et al., 2016; Lagos and Stein, 2017). The protein content of raw materials is one of the parameters routinely determined by the feed industry and is crucial for ensuring the proper composition of the matrix in feed formulations.

From this perspective, even small 1% changes in the use of protein sources during ration formulation can ultimately result in significant financial implications. The factors determining economic value are not merely the amount of crude protein, but rather the precise biochemical analyses of the digestible amino acids and metabolic energy included in the ration matrix.

Laboratory analyses

The objective of this project is to determine the differences in the nutrient composition, amino acid profile, and protein quality of soybean meal imported from various countries and used in feed production for animal nutrition. Soybean meal imported from five different countries — the United States, Brazil, Nigeria, Ukraine, and Uruguay — was used as the study material. The levels of dry matter, crude ash, crude fat, crude protein, starch, sugar, crude fiber, and digestible crude protein were determined in these meals, and the metabolic energy value for poultry was calculated using the obtained data. To determine protein quality, analyses were conducted regarding the amino acid profile, urease activity, protein distribution index, protein solubility in potassium hydroxide, and trypsin inhibitor activity.

As shown in Figure 2, meal from various origins — including the United States, Brazil, Nigeria, Ukraine, and Uruguay — was obtained from a private supplier.

The average KOH (potassium hydroxide) protein solubility values of soybean meal sourced from different countries are shown in Table 1. Based on this parameter, it was determined that the KOH value of the Ukrainian meal was the highest (79.02%), while that of the Brazilian meal was the lowest (70.27%) (P <0.001).

Based on the findings, the relatively low KOH protein solubility values observed in samples originating from Brazil (70.27%) and Uruguay (72.56%) are assessed to be related to structural characteristics directly attributable to their origin, rather than the intensity of industrial heat treatments (roasting/cooking). This variation is rooted in agro-ecological, genetic, and geographical factors.

First, the protein subunit compositions and hydrophobicity levels of genotypes cultivated in South American locations exhibit structural differences. This genetic variation is the primary factor determining the natural solubility capacity in alkaline solvents, independent of process conditions. Second, agro-ecological conditions—such as temperature, precipitation patterns, and soil composition—to which the plant is exposed during its growth stages directly affect the thermal stability and natural conformation of proteins, thereby limiting their baseline solubility limits. Additionally, region-specific harvesting and storage dynamics can also lead to permanent modifications in the stability of the protein matrix.

Data on the amino acid profiles of soybean meal are presented in Table 1. It was found that the alanine and arginine content in the Nigerian soybean meal was higher than in the other meals, at 2.28% and 3.29%, respectively (P <0.05). It was also determined that the Brazilian and Nigerian meal samples contained higher amounts of aspartic acid and glutamic acid compared to the other meal samples (P <0.05). In the analysis of methionine content, it was found that the Brazilian meal had a higher content (0.31%) while the Uruguayan meal had a lower value (0.19%) (P <0.001). It was found that the Nigerian meal had a richer content of ornithine, phenylalanine, proline, and tyrosine (P <0.05).

The amino acid profile of soybean meal observed in this study is similar to the results reported by Goldflus et al. (2006), Thakur and Hurburgh (2007), Medic et al. (2014), and Lagos and Stein (2017), and the geographical characteristics of the growing region and cultivation conditions are among the factors determining the amino acid content of the meal. In addition, there are research findings suggesting that the protein level of the meal also affects the amino acid profile (Medic et al., 2014; Mourtzinis et al., 2017; Pfarr et al., 2018).

Conclusion

In conclusion, it has been demonstrated that the country of origin of soybean meal affects its protein quality through its nutrient content and amino acid profile. Among the soybean meals examined, the Brazilian meal was found to have the highest crude protein and metabolizable energy content. Furthermore, in terms of methionine, the soybean meal from Brazil was found to have a higher content. The soybean meal from Nigeria was observed to have the highest digestibility, while urease activity was found to be at the lowest level in the soybean meals from the United States and Ukraine. In light of all these findings, it was determined that the soybean meal of Brazilian origin is more advantageous in terms of protein and methionine content, while the soybean meal of Ukrainian origin is more advantageous in terms of protein quality (urease activity, protein distribution index, protein solubility in potassium hydroxide, and trypsin inhibitor activity). Therefore, it was concluded that when using soybean meal of different origins in commercial feed production, different nutrient matrices should be employed based on these criteria.

Author: 
Güner Gövenç
Bursa Uludağ University,
Institute of Science, Department of Feeds and Animal Nutrition,
Nilüfer, Bursa, Turkey
e.mail: guner.govenc@hotmail.com